This is a crop from a recent shot for a book I am working on. ISO 100. It was shot in RAW and converted in ACR. This is obviously a high dynamic range situation I exposed for the islands but had to lighten up shadows to see the boy. The only editing that's been done here was to move the shadow slider and to increase the exposure overall by .3 stops - and as you can see, things got ugly fast.

Do you mind to post CR2 file somewhere and I can show you with proper processing, it will look much better.

A simply way is just to mount a flashgun on your 5DIII and shoot in fill-flash that effectively solves the issue

This is an example of what makes me nervous when shooting cameras with shadow noise issues, and what brought on the Nikon purchase. The Sony sensors are leagues more graceful on shots like this one, where there's no time to get a reflector or add lighting to even out the dynamic range.

I still see sky (highlight) is overblown. So you seem like to expose on highlight and pushing shadows many stops back. Sure Sony sensors are much better if you do this way, but this is not a good way to generate photos.

But that doesn't mean you cannot do with Canon cameras if you exposed properly such as increase +0.5 EV from your original photo, recover highlight in remote scene and push shadow moderately. Need some processing nevertheless.

In my book, this issue is MUCH more important than, "well gee, I bought the most expensive/sharpest lens I could find. DxO said the 24-70..." Sharpness of lenses/resolution of chip are minor footnotes compared to this, IMO:

Both are important. But let me show you how my 5DIII deals with such contrast scene.

OOC RAW

processed

The Victoria Falls at noon near-Equator harsh light. Left side is under very bright sunlight while right side is in pretty dark shadow. By exposing at middle, I am still able to recover highlight at left side and pull shadows at right side and I even recover even more brighter Falls' water with proper processing.

The Victoria Falls, Zambia

A few more samples that all are very contrast scenes. And yeah the peerless 24-70L/2.8 II shines

Cape Town, South Africa

sunset Zambezi River, Zambia without using any filter, taken from a moving fishing boat hand-held

If you believe you can get photos by exposing on highlight and then pushing deep shadows many stops back (where Sony sensor indeed has a big advantage), good luck. This is not a good method and only result surreal looking photo, that is well debated.